under terrestrial conditions, these compounds would immediately fall apart. Why doesn't this happen in space? Because in order for the two atoms in this molecular ion complex to come apart, you would need to violate some conservation principle (energy, momentum, angular momentum). In order to violate it, you would need to transfer this quantity to another particle. In terrestrial conditions there are plenty plenty plenty of 'other particles' around to do this process; not so much in space.
It totally surprised me when I read the article, but your comment makes sense. If there aren't opportunities to disrupt the equilibrium from collisions, molecules with Noble gases can be stable.
After posting, I learned that argon fluorohydride has been synthesized in the lab and is stable up to 40 degrees Kelvin.
